Intravascular probes which include ultrasound imaging crystals are well known. For example, it has previously been proposed to mount a piezoelectric crystal element (conventionally termed a "transducer") on or within a catheter of the type which can be inserted into a blood vessel. Once the probe has been inserted into a blood vessel, the transducer is electro-mechanically excited (as by the application of an electrical signal) to cause emission of ultrasonic energy into the surrounding tissue. While much of the emitted energy is absorbed and scattered by the surrounding tissue, a sufficient amount of energy is reflected back toward the transducer to permit imaging (with reflection occurring principally at the interfaces between different types of biological material, e.g., the interface between blood and the vascular wall, the interface between blood and lesions adhered to the vascular wall etcetera).
The transducer, in turn, produces weak electrical signals in response to electro-mechanical excitation by the returning reflected ("echo") ultrasonic energy. These weak electrical signals can be used to determine the geometry and/or other characteristics of the blood vessel, for example, to determine whether or not the blood vessel contains lesions or other abnormalities. These determinations are usually termed "imaging" since suitable video and/or other signal monitoring equipment are employed to convert the weak electrical signals produced by the transducer into human-readable form. Information gained from such imaging thus may assist the physician in a vascular treatment in real time or in diagnosing a patient's particular ailment or disease so that suitable therapy can be prescribed.
Intravascular imaging through 360.degree. has also been proposed. For example, in the above-referenced U.S. Pat. No. 4,841,977, novel intravascular ultrasonic imaging probes are disclosed having transducer arrays which include radially spaced-apart transducers. These radially spaced apart transducers thereby image corresponding radial segments of the vessel interior under examination (with conventional algorithms being utilized when necessary to "fill in" missing image segments through interpolation and/or partial images to provide sufficient information to a viewer).
It has also recently been proposed in U.S. Pat. No. 4,794,931 to Yock to provide intravascular imaging probes with a stationary transducer and an ultrasonic wave reflector which is rotatable and longitudinally movable relative to the transducer. (See, FIGS. 10 and 11 of Yock '931, and the corresponding description thereof). Moreover, it will be observed that the imaging devices disclosed in Yock '931 are each provided with a forwardly extending guide wire which serves to guide or steer the housing (which includes the transducer and reflection mirror) as the probe is introduced into the vessel of the patient's vascular system.
The use of laser energy as a means of performing surgical procedures is also well known as evidenced by U.S. Pat. Nos. 4,785,805 to Joffe et al; 4,641,912 to Goldenberg; 4,760,845 to Kovalcheck; 4,765,330 to Bach; and 4,785,806 to Deckelbaum. In general, all of these prior art laser surgery devices employ a laser guide as a means for guiding laser energy to a distal portion of the probe, where it is emitted and used to ablate afflicted tissue.
In U.S. Pat. No. 4,672,963 to Barken, a system which employs ultrasonic imaging techniques and laser ablation techniques has been proposed. In the system of Barken '963, however, separate discrete probes respectively dedicated to performing ultrasonic imaging and laser ablation procedures are employed.
Recently, a probe assembly which integrates ultrasonic imaging and laser ablation techniques has been proposed in U.S. Pat. No. 4,576,177 to Webster, Jr. In one embodiment of the probe disclosed in this patent (see FIG. 1), a disc-shaped piezoelectric crystal is positioned at a distal end of a catheter and is disposed at an angle relative to the catheter axis so as to direct ultrasonic signals generated thereby towards the blood vessel wall. An optical fiber extends the length of the catheter and terminates in operative association with a microlens which is said to change the direction of the laser irradiation to about the center of, and in the same general direction as, the transmitted ultrasonic signal (see, column 5, lines 16-30 in Webster, Jr. '177).
In distinct contrast to the probe assemblies of the prior art, the preferred probe assemblies of the present invention direct the ultrasonic imaging waves and laser radiation along an essentially common path, but in opposing axial directions, towards a reflective surface interposed therebetween. The incident ultrasonic waves and laser radiation is therefore redirected generally radially of the probe along respective radial paths. By rotating the operative elements (e.g., the reflective surface and/or the housing which contains it in addition to the terminal end of the optical fiber and the ultrasonic transducer), 360.degree. imaging and laser ablation can be accomplished.
Further aspects and advantages of the present invention will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiments thereof which follow.